AM60镁合金在侵蚀性溶液中的电化学阻抗分形(英文)

Electrochemical Impedance Fractal Study of AM60 Magnesium Alloy in Aggressive Solution

研究了AM60镁合金在0.1 mol/L NaCl,Na2SO4和饱和Mg(OH)2溶液中浸泡96小时的电化学阻抗谱(Electrochemical impedance spectroscopy,EIS)行为。溶液中含有Cl-时,阻抗谱呈现高中频两个容抗弧和低频感抗成分,且低频感抗组分在浸泡36小时后消失。AM60浸泡在Na2SO4溶液中具有类似的电化学阻抗行为,区别在于低频弛豫过程和容抗大小。相比于Cl-离子,SO42-离子具有相对较弱的腐蚀进攻能力。在饱和Mg(OH)2溶液中,由于Mg(OH)2弱水解有效抑制了阴阳极反应(极化曲线结果),EIS谱图仅有中高频两个容抗弧,没有对应孔核形成和消失的低频感抗行为。由于高频容抗弧对应AM60原表面的双电层信息,其弥散系数n、分形维数DE可以获取腐蚀过程中的细节信息。阻抗分形维数DE随时间的变化曲线结果表明Cl-具有最强的腐蚀进攻性,同时也具有再钝化效应,以修复由于Cl-进攻形成的孔核。SO42-离子腐蚀进攻性相对较弱,且没有再钝化现象。饱和Mg(OH)2溶液中DE的增加主要是由于不溶性Mg(OH)2沉积吸附在镁合金表面,增加表面的粗糙度。

Electrochemical impedance spectroscopy （EIS） was carried out On AM60 magnesium alloy specimens during 96 hour exposure periods into aerated 0. 1mol/L NaCl, 0. 1mol/L Na2SO4 and saturated Mg（OH）2 solutions. In the solutions containing Clˉ ions, the impedance spectroscopy takes on two capacitive loops in high frequency and middle frequency domain respectively, while one inductive loop appears in first 36 hour immersion. The similar EIS behavior for AM60 in NazSO4 solution had been observed, while the low frequency relaxation behavior is ＂different. Comparing to the Clˉ ions, the SO4^2- ions presented relatively weak corrosive ability. In the saturated Mg（OH）2 solution, due to the anodic and cathodic reaction were restrained from the polarization curves by weak hydrolyzation of Mg（OH）2, the EIS behavior of AM60 differs from that in the other two aggressive ions solution. A relatively new method was applied to research the corrosion process with detail. Fractal dimension was calculated from the high frequency capacitive arc which was corresponding to the origin surface double electronic layer of AM60 magnesium in three kind solutions. The curves of fractal dimension vs immersion time indicated that Clˉ ions presented the strongest corrosive attack, also shown the best self-repassivation behavior to recover the pits which were produced by the existefice of Clˉ ions. The SO4^2- ions attacked the surface of AM60, while the repassivation could be ignored. The increase of fractal dimension in Mg（OH）2 was mainly due to the adsorption of infusibility Mg（OH）2 on the surface increasing surface roughness.